Apparatus and methods for robot assisted bone treatment

ABSTRACT

A method for performing a surgical procedure includes planning a resection of a bone of a patient. A volume of the bone is removed according to the planned resection using a surgical tool. As the bone is removed, data corresponding to a shape and volume of the removed bone is tracked with a computer system operatively coupled to the surgical tool. A prosthesis is implanted onto the bone of the patient based on the tracked data corresponding to the shape of the removed bone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/546,498, filed Aug. 21, 2019, which is a continuation of U.S. Pat.No. 10,433,921, filed Dec. 19, 2016, which claims the benefit of thefiling date of U.S. Provisional Application No. 62/271,599, filed Dec.28, 2015, the disclosures of which are hereby incorporated by referenceherein.

BACKGROUND OF THE DISCLOSURE

The functions of a computer-assisted surgery (CAS) system may includepre-operative planning of a procedure, presenting pre-operativediagnostic information and images in useful formats, presenting statusinformation about a procedure as it takes place, and enhancingperformance. The CAS system may be used for procedures in traditionaloperating rooms, interventional radiology suites, mobile operating roomsor outpatient clinics.

Navigation systems may be used to display the positions of surgicaltools with respect to preoperative or intraoperative image datasets.These images may include two-dimensional fluoroscopic images, andthree-dimensional images generated using, for example, magneticresonance imaging (MRI), computed tomography (CT) and positron emissiontomography (PET). Some navigation systems make use of a tracking orlocalizing system. These systems locate markers attached or fixed to anobject, such as an instrument or a patient, and track the position ofmarkers. These tracking systems may be optical and/or magnetic, but mayalso include acoustic and/or ultrasonic systems. Optical systems mayhave a stationary stereo camera pair that observes passive reflectivemarkers or active infrared LEDs attached to the tracked tools. Magneticsystems may have a stationary field generator that emits a magneticfield that is sensed by small coils integrated into the tracked tools.

Most navigation systems transmit information to the surgeon via acomputer monitor. Conversely, the surgeon transmits information to thesystem via a keyboard and mouse, touchscreen, voice commands, controlpendant, or foot pedals, and also by moving the tracked tool. The visualdisplays of navigation systems may display multiple slices throughthree-dimensional diagnostic image datasets.

Autonomous robots have been applied commercially to joint replacementprocedures. These systems make precise bone resections, improvingimplant fit and placement relative to techniques that rely on manualinstruments. Robots may also utilized haptic feedback systems to providefor semi-autonomous control, as described in greater detail below.Registration is performed by having the robot touch fiducial markersscrewed into the bones or a series of points on the bone surfaces.Cutting is performed autonomously with a high-speed bur, although thesurgeon can monitor progress and interrupt it if necessary. Bones may beclamped in place during registration and cutting, and are monitored formotion, which then requires re-registration.

Despite the advances in robotic devices and methods to perform or assistin the performance of certain surgeries, further advances are stilldesirable. For example, while robotic systems have been used to resect apatient's bone, it would be desirable to integrate the same robot intorelated procedures, such as in creating and/or applying a bone graft.

BRIEF SUMMARY OF THE INVENTION

According to a first embodiment of the disclosure, a method ofperforming a surgical procedure on a patient includes planning aresection of a bone of the patient, and removing a volume of the bonewith a surgical tool according to the planned resection. Datacorresponding to a shape and volume of the removed bone is tracked witha computer system operatively coupled to the surgical tool, and aprostheses is implanted onto the bone of the patient based on thetracked data corresponding to the shape and volume of the removed bone.

The surgical tool for removing the volume of the bone may be operativelycoupled to a robotic device during the removal step. The surgical toolmay be a manual tool. The implanted prosthesis may be deposited on thebone with a deposition tool operatively coupled to a robotic deviceduring the implanting step. The deposition tool may be a syringe device.The implanted prosthesis may be an ultraviolet curable resin. Atemperature of the prosthesis may be monitored during the implantingstep.

The implanting step may further include forming a lattice on theresected bone with a first deposition tool containing a first prosthesistherein, with the first deposition tool being operatively coupled to arobotic device, and filling the lattice with a second prosthesis, whichmay contained in a second deposition tool operatively coupled to therobotic device.

The implanting step may further include implanting a first prosthesislayer on the resected bone with a first deposition tool operativelycoupled to a robotic device, the first prosthesis layer having a firstdensity, and implanting a second prosthesis layer on the firstprosthesis layer, which may be done with a second deposition tooloperatively coupled to a robotic device, the second prosthesis layerhaving a second density different than the first density. The seconddensity may be greater than the first density.

The method may further include shaping the prosthesis using the surgicaltool so that the prosthesis has a shape complementary to the shape ofthe removed bone. The surgical tool may be selected from one of thegroup consisting of a bur, saw, laser, cautery device, and waterjet.During the step of shaping the prosthesis, the prosthesis may be securedto a holding device. The step of removing the volume of the bone mayinclude forming a first geometric shape in the bone and the step ofshaping the prosthesis includes forming a second geometric shape in theprosthesis, the first geometric shape being keyed to the secondgeometric shape. The first and second geometric shapes may form adovetail configuration. The step of implanting the prosthesis onto thebone of the patient may include coupling the prosthesis onto the bonewith a fastener. The fastener may be selected from the group consistingof bone screws and bone pins. A feature for accepting the fastener maybe formed into at least one of the bone and the prosthesis. The featuremay be selected from one of the group consisting of a threaded screwhole and pilot hole. The step of shaping the prosthesis using thesurgical tool may include forming a plurality of discrete prostheses,and the step of implanting the prosthesis onto the bone may includeimplanting each of the discrete prostheses.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary operating room inwhich a haptic device is used with a computer-assisted surgery system.

FIG. 2 is a flowchart of a surgical method according to one aspect ofthe disclosure.

FIG. 3A illustrates an image of a bone to be treated by a surgicalprocedure according to one aspect of the disclosure.

FIG. 3B illustrates an aspect of a surgical plan for the bone of FIG.3A.

FIG. 3C is a highly schematic representation of the haptic device ofFIG. 1 performing a resection on the bone of FIG. 3A.

FIG. 3D is a highly schematic representation of the haptic device ofFIG. 3C replacing the bone resected in FIG. 3A.

FIG. 3E is a highly schematic representation of the haptic device ofFIG. 3C replacing the bone resected in FIG. 3A according to anotheraspect of the disclosure.

FIG. 4A illustrates an image of a bone to be treated by a surgicalprocedure according to an aspect of the disclosure.

FIG. 4B illustrates a donor bone secured within a holding system for usein treatment of the bone of FIG. 4A.

FIG. 4C illustrates an aspect of a surgical plan for the bone of FIG.4A.

FIG. 4D is a highly schematic representation of the haptic device ofFIG. 1 performing a resection on the bone of FIG. 4A.

FIG. 4E is a highly schematic representation of the haptic device ofFIG. 1 performing a resection on the donor bone of FIG. 4B.

DETAILED DESCRIPTION

FIG. 1 is a diagrammatic illustration of an exemplary operating room inwhich a haptic device 113 is used with a computer-assisted surgerysystem 11. Computer-assisted surgery system 11 may include a displaydevice 30, an input device 34, and a processor based system 36, forexample a computer. Input device 34 may be any suitable input deviceincluding, for example, a keyboard, a mouse, or a touch screen. Displaydevice 30 may be any suitable device for displaying two-dimensionaland/or three-dimensional images, for example a monitor or a projector.If desired, display device 30 may be a touch screen and be used as aninput device. One example of a system incorporating a haptic device 113is described in greater detail in U.S. Pat. No. 7,831,292, the entiredisclosure of which is hereby incorporated by reference herein.

Haptic device 113 is, in the illustrated example, a robotic device.Haptic device 113 may be controlled by a processor based system, forexample a computer 10. Computer 10 may also include power amplificationand input/output hardware. Haptic device 113 may communicate withcomputer-assisted surgery system 11 by any suitable communicationmechanism, whether wired or wireless.

Also shown in FIG. 1 is a storage medium 12 coupled to processor basedsystem 36. Storage medium 12 may accept a digital medium which storessoftware and/or other data. A surgical tool or instrument 112 is showncoupled to haptic device 113. Surgical tool 112 is preferablymechanically coupled to haptic device 113, such as by attaching orfastening it. However, if desired, surgical tool 112 may be coupled,either directly or indirectly, to haptic device 113 by any othersuitable method, for example magnetically. Surgical tool 112 may behaptically controlled by a surgeon remotely or haptically controlled bya surgeon 116 present in proximity to surgical tool 112, althoughautonomous control with surgeon oversight is possible as well. Surgicaltool 112 may be, for example, a bur, saw, laser, waterjet, cautery tool,or other trackable tool capable of cutting or otherwise shaping orresecting patent tissue, including bone. Patient tissue and bone may bereferred to interchangeably herein and may include cartilage, tendons,skin tissue, and/or bone whether it be cortical or cancellous bone.

Haptic object 110 is a virtual object used to guide and/or constrain themovement and operations of surgical tool 112 to a target area inside apatient's anatomy 114, for example the patient's leg. In this example,haptic object 110 is used to aid the surgeon 116 to target and approachthe intended anatomical site of the patient. Haptic feedback forces maybe used to slow and/or stop the surgical tool's movement if it isdetected that a portion of surgical tool 112 will intrude or cross overpre-defined boundaries of the haptic object. Furthermore, hapticfeedback forces can also be used to attract (or repulse) surgical tool112 toward (or away from) haptic object 110 and to (or away from) thetarget. If desired, surgeon 116 may be presented with a representationof the anatomy being operated on and/or a virtual representation ofsurgical tool 112 and/or haptic object 110 on display 30.

The computer-assisted surgery (“CAS”) system preferably includes alocalization or tracking system that determines or tracks the positionand/or orientation of various trackable objects, such as surgicalinstruments, tools, haptic devices, patients, donor tissue and/or thelike. The tracking system may continuously determine, or track, theposition of one or more trackable markers disposed on, incorporatedinto, or inherently a part of the trackable objects, with respect to athree-dimensional coordinate frame of reference. Markers can takeseveral forms, including those that can be located using optical (orvisual), magnetic or acoustical methods. Furthermore, at least in thecase of optical or visual systems, location of an object's position maybe based on intrinsic features, landmarks, shape, color, or other visualappearances, that, in effect, function as recognizable markers.

Any type of tracking system may be used, including optical, magnetic,and/or acoustic systems, which may or may not rely on markers. Manytracking systems are typically optical, functioning primarily in theinfrared range. They may include a stationary stereo camera pair that isfocused around the area of interest and sensitive to infrared radiation.Markers emit infrared radiation, either actively or passively. Anexample of an active marker is a light emitting diode (LED). An exampleof a passive marker is a reflective marker, such as ball-shaped markerwith a surface that reflects incident infrared radiation. Passivesystems may include an infrared radiation source to illuminate the areaof focus. A magnetic system may have a stationary field generator thatemits a magnetic field that is sensed by small coils integrated into thetracked tools.

With information from the tracking system on the location of thetrackable markers, CAS system 11 may be programmed to be able todetermine the three-dimensional coordinates of an end point or tip of atool and, optionally, its primary axis using predefined or known (e.g.from calibration) geometrical relationships between trackable markers onthe tool and the end point and/or axis of the tool. A patient, orportions of the patient's anatomy, can also be tracked by attachment ofarrays of trackable markers. In the illustrated example, the localizeris an optical tracking system that comprises one or more cameras 14 thatpreferably track a probe 16. As shown in FIG. 1 , cameras 14 may becoupled to processor based system 36. If desired, cameras 14 may becoupled to computer 10. Probe 16 may be a conventional probe. Ifdesired, the probe may be rigidly attached to haptic device 113 orintegrated into the design of haptic device 113.

In one implementation, processor based system 36 may include imageguided surgery software to provide certain user functionality, e.g.,retrieval of previously saved surgical information, preoperativesurgical planning, determining the position of the tip and axis ofinstruments, registering a patient and preoperative and/orintraoperative diagnostic image datasets to the coordinate system of thetracking system, etc. Full user functionality may be enabled byproviding the proper digital medium to storage medium 12 coupled tocomputer 36. The digital medium may include an application specificsoftware module. The digital medium may also include descriptiveinformation concerning the surgical tools and other accessories. Theapplication specific software module may be used to assist a surgeonwith planning and/or navigation during specific types of procedures. Forexample, the software module may display predefined pages or imagescorresponding to specific steps or stages of a surgical procedure. At aparticular stage or part of a module, a surgeon may be automaticallyprompted to perform certain tasks or to define or enter specific datathat will permit, for example, the module to determine and displayappropriate placement and alignment of instrumentation or implants orprovide feedback to the surgeon. Other pages may be set up to displaydiagnostic images for navigation and to provide certain data that iscalculated by the system for feedback to the surgeon. Instead of or inaddition to using visual means, the CAS system could also communicateinformation in other ways, including audibly (e.g. using voicesynthesis) and tactilely, such as by using a haptic interface. Forexample, in addition to indicating visually a trajectory for a drill orsaw on the screen, a CAS system may feed information back to a surgeonwhether he is nearing some object or is on course with an audible sound.To further reduce the burden on the surgeon, the module mayautomatically detect the stage of the procedure by recognizing theinstrument picked up by a surgeon and move immediately to the part ofthe program in which that tool is used.

The software which resides on computer 36, alone or in conjunction withthe software on the digital medium, may process electronic medicaldiagnostic images, register the acquired images to the patient'sanatomy, and/or register the acquired images to any other acquiredimaging modalities, e.g., fluoroscopy to CT, MRI, etc. If desired, theimage datasets may be time variant, i.e. image datasets taken atdifferent times may be used. Media storing the software module can besold bundled with disposable instruments specifically intended for theprocedure. Thus, the software module need not be distributed with theCAS system. Furthermore, the software module can be designed to workwith specific tools and implants and distributed with those tools andimplants. Moreover, CAS system can be used in some procedures withoutthe diagnostic image datasets, with only the patient being registered.Thus, the CAS system need not support the use of diagnostic images insome applications—i.e. an imageless application.

Haptic device 113 may be used in combination with the tracking andimaging systems described above to perform highly accurate boneresections and grafting bone on the resected bone. A general descriptionof such a procedure is described below, followed by at least twoparticular examples of the procedure.

FIG. 2 illustrates a flow chart of a surgical procedure according to thepresent disclosure. In a first step 200, a physician or other medicalpractitioner diagnoses that a patient would benefit from having aportion of a bone removed or resected followed by implantation of aprosthesis onto the bone at or near the site of resection. In thisregard, the term prosthesis encompasses transplanted bone including, forexample, allograft, autograft, xenograft, or bone substitute as well asother biologics, metals, plastics, and combinations thereof. Afterdetermining the intended surgical site, the surgical site may be imagedin step 210, for example via an MRI or CT scan, or any other suitableimaging modality. The images may be uploaded or otherwise transferred toprocessor based system 36 for use on the software residing therein.Three-dimensional models of individual bones and/or joints may becreated from the images taken of the surgical site. Systems and methodfor image segmentation in generating computer models of a joint toundergo arthroplasty is disclosed in U.S. Pat. No. 8,617,171, the entiredisclosure of which is hereby incorporated by reference herein. Theimages may be processed or otherwise used in order to plan portions ofthe surgical procedure in step 220. In one example, the desired geometryand/or volume of the bone to be removed or resected may be defined basedon the images. The surgeon may define the geometry and/or volume usingthe software with manual definition or semi-automatic definition. Forexample, the surgeon may outline geometric boundaries on the images ondisplay 30 with input device 34, such as a mouse, to determine thegeometry and/or volume of bone to be removed. In addition oralternatively, the software may employ image processing to identifydamaged areas of the bone, for example by determining bone quality, forexample by analyzing bone density based on brightness or otherparameters of the image, to provide for a suggested geometry and/orvolume of bone removal which may be confirmed or altered by the surgeon.It should be understood that this geometry and/or volume definition step220 may be performed prior to the surgical procedure on a separatecomputer system, with the results of this step imported to processorbased system 36. It should also be understood that the steps shown inFIG. 2 do not necessarily need to be completed in the order shown. Forexample, a patient may be first imaged in step 210, and based on theresults and analysis of the imaging, the determination that surgicalintervention is required in step 200 may be made.

In step 230, the surgeon may define the boundaries of haptic object 110.This may be accomplished in one of several ways. In one example, thehaptic object 110 may be based on the geometry and/or volume of bone tobe removed determined in step 220. The haptic object 110 may be definedto have boundaries along the geometry and/or volume of bone to beremoved so that the surgical tool 112, as described above, may aid thesurgeon 116 to target and approach the intended anatomical site of thepatient with surgical tool 112. In another example, a number ofpre-defined shapes or volumes may be pre-loaded into computer 10 and/orcomputer 36. For example, different procedures may have certain typicalshapes or volumes of intended bone removal, and one or more pre-loadedgeometries and/or volumes may be included in the software application oncomputer 10 and/or computer 36, for example with each geometry and/orvolume corresponding to one or more types of procedures. Thesepre-loaded shapes or volumes may be used without modification, but inmany cases the pre-loaded geometries and/or volumes will be modified bythe surgeon and/or combined with other pre-loaded geometries and/orvolumes to meet the needs of the particular patient.

In step 240, haptic device 113 is registered to the anatomy of thepatient. If desired, a representation of the anatomy of the patientdisplayed on display device 30 may also be registered with the anatomyof the patient so that information in diagnostic or planning datasetsmay be correlated to locations in physical space. For example, thehaptic device 113 (or a probe attached thereto) may be directed to touchfiducial markers screwed into the bones, to touch a series of points onthe bone to define a surface, and/or to touch anatomical landmarks. Theregistration step 240 is preferably performed when the anatomy isclamped or otherwise secured from undesired movement. Registration mayalso be performed using, for example, intraoperative imaging systems.However, the anatomy does not need to be clamped in certain situations,for example if tracking devices are coupled to the anatomy. In thatcase, any movement of the anatomy is tracked so that rigid fixation isnot necessary.

In step 250, with patient registration complete, the bone removalprocedure is performed. The procedure may be any suitable procedure inwhich bone is to be removed, such as resection in preparation for jointreplacement, bulk bone removal, or small volume bone removal fortreating small tumors or the like. The actual process of removing bonemay be performed semi-autonomously under haptic control, as describedabove, autonomously by haptic device 113, manually via free-handresection by the surgeon, or any combination of the above. Regardless ofthe specific procedure or the level of surgeon control, the bone removalgeometry and/or volume is tracked by computer 10 (and/or computer 36) bytracking the position of surgical tool 112 with the navigation systemand/or joint encoders of haptic device 113. Thus, even if the boneactually removed differs from the surgical plan, the computer 10 (and/orcomputer 36) tracks and stores information relating to the bone actuallyremoved. In other embodiments, photo and/or pressure sensors may beemployed with haptic device 113 to precisely measure the geometry and/orvolume of bone that is removed. It is also contemplated that, followingthe bone removal, additional imaging may be performed and compared topatient images prior to the resection to determine bone actuallyremoved, which may be used as an alternative to the robotic tracking ofbone removal or as confirmation of same. Still further, instead oftracking and storing information to the bone actually removed during theremoval process, the bone may first be removed, and following the boneremoval, the remaining surface of the bone may be probed to register theprecise remaining volume and/or geometry of bone.

With the information relating to the geometry and/or volume of boneremoved from the patient, computer 10 and/or computer 36 determines theprecise three-dimensional geometry of the prosthesis to be implantedinto or onto the bone in step 260. Based on this determination, hapticdevice 113 may be used in any one of a number of ways to form and/orplace the prosthesis. For example, if the prosthesis is an allograftbone, haptic device 113 may employ the determined geometry and/or volumeto assist the surgeon in shaping the allograft bone to precisely fit thegeometry of the resected bone. Alternately, a similar procedure may beused on the patient if the prosthesis is an autograft bone taken fromanother bone portion of the patient, with the haptic device 113providing assistance to the surgeon in resecting the precise geometryand/or volume of autograft to replace the bone removed in step 250. Inother embodiments, haptic device 113 may be employed to resect moreautograft than will be needed to replace the bone removed in step 250while taking into account whether such removal of autograft taken fromthe another bone portion of the patient is safe for the patient. Stillfurther, a liquid or putty-type bone graft may be applied to the site ofbone removal in step 250, for example by attaching a syringe-like deviceas the tool of haptic device 113, with precise application of the bonegraft to the site of bone removal. Some of these examples are describedin greater detail below.

As noted above, steps 200 through 260 do not necessarily need to beperformed in the order shown in FIG. 2 . For example, in some cases, itmay be preferable to prepare the prosthesis prior to resecting thepatient's bone. This may be true in the case of an autograft prosthesissince the donor tissue maybe limited and/or difficult to access. In sucha case, the autograft may be prepared according to the surgeon'sexperience (manually or otherwise), the intended surgical procedure,and/or any pre- and intra-operative planning Once the prosthesis isformed, the prosthesis may be probed and registered to using computer 10and/or computer 36 so that the volume and/or geometry of the prosthesisis stored. The volume and/or geometry of the prosthesis may then be usedto create the haptic object 110, so that the surgeon may use the hapticdevice 113 to resect the patient's bone to a shape corresponding to thegeometry and/or volume of the previously prepared prosthesis.

One particular example of a procedure utilizing steps 200-260 of FIG. 2is for treating interlesional bone tumors. Common types of such bonetumors that may be treated according to the below procedure may includegiant cell tumors of bone, benign aneurysmal bone cysts, and malignantlow grade chondrosarcomas. The patient's bone, including the tumor site,is imaged in step 210. A highly schematic illustration of an image 300of a patient's femur 305 is shown in FIG. 3A with a bone tumor(s) 310shown on the image. The image 300, or a set of images 300, may beuploaded or otherwise stored on processor-based system 36.

The processor-based system 36, for example with the aid of software, mayautomatically identify the location and/or boundaries of tumors(s) 310.In one example, this determination is based on bone density and/orquality information from the image 300. Tumor(s) 310 and surroundingportions of healthy femur 305 may have different density values,allowing for the correlation of image brightness to bone density inorder to determine the boundaries between tumor(s) 310 and adjacentportions of healthy femur 305. The surgeon may review and confirm thedetermined location of tumor(s) 310, revise the determined location ofthe tumor(s), or otherwise manually identify the location of thetumor(s).

Based on the determination of the boundary between tumor(s) 310 andhealthy femur 305, the processor-based system 36 may automaticallydetermine the geometry and/or volume 315 of femur 305 to be resected toeffectively remove tumor(s) 310, as provided by step 220 and as shown inFIG. 3B. In one example, the processor-based system 36 may apply athree-dimensional buffer around the determined boundary between tumor(s)310 and healthy femur 305, for example a buffer of 0.5 mm, 1 mm, 2 mm,or 3 mm outside the boundary to help ensure that the removal of tumor(s)310 is complete. In other examples, the software-based system 36 mayprovide a standard buffer, for example 1 mm, and the surgeon may confirmthe buffer or revise the buffer. Still further, the surgeon may manuallyinput the geometry and/or volume of bone to be removed, using his or herdiscretion regarding any appropriate buffer beyond the determinedlocation of tumor(s) 310. Based on the geometry and/or volume 315 ofbone to be removed, the system may determine a haptic object 110correlating to the geometry and/or volume 315 as provided in step 230.As described in greater detail below, it is also contemplated that thesurgeon may skip the step of defining the volume of bone to be removed,rather using his or her own experience to resect the bone to removetumor(s) 310 using haptic device 113. As is described in greater detailbelow, the resection may alternately be a manual resection procedure.

Whether or not steps 220 and 230 are performed, the patient is thenregistered to the haptic device 113 as described above in connectionwith step 240. A surgical tool 112 in the form of a small bur may becoupled to haptic device 113 and used to remove the tumor(s) 310 onfemur 305. If steps 220 and 230 were performed, the haptic device 113may autonomously or semi-autonomously guide the bur using theconstraints of the haptic object 110 to remove the desired geometryand/or volume 315 of bone, as shown in FIG. 3C. If steps 220 and 230were not performed, the surgeon may manually guide the bur throughmanipulation of the haptic device 113. In either scenario, the path ofthe bur is tracked and information regarding the actual volume of boneremoved is stored in computer 10 (and/or computer 36). Preferably, thetip and/or sides of the bur, or any relevant cutting surfaces, aretracked. It is further contemplated that, if steps 220 and 230 are notperformed, a manual device, such as a curette, may be employed by thesurgeon to remove the tumor(s) 310. The curette may be provided with atracking array and be operatively coupled to computer 10 (and/orcomputer 36) so that the movements of the curette in space relative tothe patient's bone are tracked, so that the precise volume of boneremoved may be tracked for use in replacing the removed bone. For eachexample above, because the three-dimensional position of the patient'sbone is known via registration and the image(s) 300, and thethree-dimensional position of the surgical tool (e.g. bur or curette) isknown via the tracking system, any time the tip of the surgical tool 112intersects with the patient's bone, the portion of bone removed may beidentified and stored by computer 10 (and/or computer 36).

In step 260, the precise geometry and/or volume of the prosthetic isdetermined. The prosthetic geometry and/or volume may be identical tothat of the bone removed, as tracked during the removal step, whetherthe bone removal was autonomous, semi-autonomous, or manual. If the boneremoval geometry and/or volume was pre-planned using computer 36, thegeometry and/or volume of the prosthetic may be identical to thegeometry and/or volume of the planned bone removal, since haptic device113 helps ensure the bone removal occurs exactly (or nearly exactly)according to plan. Instead of forming the geometry of the prosthesis tobe identical to the geometry and/or volume of the removed bone,modifications may be made, for example so that the prosthesis can have apress fit or interference fit with the patient's anatomy.

The prosthesis may take any suitable form, including, e.g.,demineralized bone matrices (“DBM”), morselized autograft, morselizedallograft, polymethyl methacrylate (“PMMA”) bone cements, syntheticcalcium phosphate or calcium sulfate based bone grafts, and/orultraviolet (“UV”) curable resins. If the prosthesis takes the form ofone of the above void fillers, it may be delivered via syringe orsyringe-like device. For example, as shown in FIG. 3D, the haptic device113 may include a surgical tool 112 in the form of a syringe-like devicepacked with void filler 320. The void filler 320 may be ejected from theend effector 112 by haptic device 113 to precisely fill the volume ofbone previously removed with the void filler 320. Alternately, the voidfiller 320 may be deposited in some other desired geometry and/or volumewithin the resected bone, such as a partial fill.

Rather than use a homogenous void filler 320, the process may be dividedinto steps to provide additional features of the prosthetic bone. Forexample, a surgical tool 112 with a syringe packed with a curable resin,such as a UV curable resin, may be coupled to haptic device 113. Acuring source, such as a UV source, may be provided along with surgicaltool 112 so that the curable resin cures contemporaneously ornear-contemporaneously upon deposition into the bone void. A cured resinlattice may be formed in this manner, which may be then be infused witha void filler or a bone growth composition. The lattice may take theform of a structural three-dimensional matrix with voids that can befilled with a void filler and/or bone growth composition. This infusionmay be accomplished by coupling a surgical tool 112 in the form of asyringe-like device packed with the bone growth material to hapticdevice 113, or manually by the surgeon.

Another alternative, as shown in FIG. 3E, is to apply a large mass ofvoid filler 320 into the void, for example manually, to partially orcompletely fill the void. If the void is completely filled with voidfiller 320, a bur or other surgical tool 112 is coupled to haptic device113, and the haptic device 113 may autonomously or semi-autonomously cutaway extraneous void filler 320 until the remaining void filler exactlymatches the geometry and/or volume of resected bone.

With any of the void filler 320 deposition techniques described above,the void filler 320 may vary in quality in three-dimensions. Forexample, layers of filler 320 which have different densities may beapplied as desired, for example by repeating the delivery described inconnection with FIG. 3D in sequential steps using different fillers withdifferent densities. This method may facilitate more closely mimickingthe natural bone, for example where inner layers of cancellous bone areless dense than outer layers of cortical bone. Other ways to achievevariable prosthesis properties such as variable density include, forexample, adding beads, mesh materials, or fibrous materials to thefiller material. Still further, different layers may be deposited in analternating fashion, such as a hard prosthesis having a liquid or fillermaterial underneath and also on top of the hard prosthesis.

Some void fillers 320, such as bone cement, may be applied to the boneat a relatively high temperature and cure as the cement cools. Thesurgical tool 112 may incorporate a thermal sensor so that computer 10(and/or computer 36) is able to detect a temperature of the void filler320 packed into the effector. The computer 10 (and/or computer 36) maythen control the deposition of the void filler 320 onto the bone so thatthe application occurs at an optimal viscosity and/or thermal optimum.For example, if the void filler 320 is too hot, the native bone may bedamaged. However, if the void filler 320 is allowed to cool too muchprior to deposition, the deposition may not be effective if the voidfiller 320 has already begun to harden.

Although the procedure above is described as tracking bone removalcoincident with the bone removal process, other alternatives may besuitable. For example, after the bone removal is complete, a shapeablematerial may be pressed into the bone void to create a mold having avolume and/or geometry corresponding to the resected bone. It should beunderstood that this mold may actually be a “reverse” mold of theresected bone, since the mold has the shape of what was removed. Themold, once formed, may be removed from the bone and the surface probedand registered to determine the shape of the removed bone (andcorrespondingly the shape of the remaining bone).

Another example of a procedure utilizing steps 200-260 of FIG. 2 is forbulk allograft procedures, which may entail replacement of largerquantities of bone than a relatively minor bur or curettage proceduredescribed above. It should be understood that, although the termallograft is used, the description may apply to autograft and/orxenograft procedures, unless explicitly described otherwise. Further,other types of prostheses, including metal and/or plastic procedures,may be used alternately to or in addition to tissue prostheses. Suchbulk allograft procedures may include bone replacement after treatinglarge tumors, treating trauma, or revisions of previously implantedprostheses, for example.

Structural bulk allograft procedures using tissue prostheses may providecertain benefits because the allograft may include soft tissueattachments to allow the surgeon to reconstruct the soft tissue with thepromise of increased restoration of function. For example, a proximaltibial allograft may include a patellar tendon, a proximal femoralallograft may include hip abductor tendons, and a proximal humeralallograft may include rotator cuff tendons.

As an example, a physician may determine that, following trauma to aproximal tibia, it would be beneficial to replace the proximal tibiawith a bulk tissue allograft from a donor. The patient's bone, includingthe trauma site, is imaged in step 210. A schematic illustration of animage 400 of a patient's tibia 405 is shown in FIG. 4A with a tibialfracture 410 shown on the image. The image 400, or a set of images 400,may be uploaded or otherwise stored on processor based system 36.

An appropriate prosthesis, such as a donor tibia 505, may be securedinto a holding device 515, as shown in FIG. 4B. In one example, theholding device 515 may include a base 520 and a plurality of clamps 525to secure the donor tibia 505 in place. Holding device 515 may be astandalone device, may be attachable to an operating room accessory suchas an operating table, a limb holder attached to the operating roomtable or the haptic device 113, or may be integrated with an operatingroom accessory such as an operating table or the haptic device 113.Instead or in addition to the holding device 515, the donor tibia 505may have one or more trackers 530 attached so that movement of the donortibia 505, intentional or not, is captured by the navigation system. Theability to use one or more trackers with the donor tibia 505 may applywith equal force to other implants described in this disclosure.

The donor tibia 505, including any soft tissue attachments, such as apatellar tendon, may be imaged if desired. In one example, imaging thedonor tibia 505 and/or soft tissue attachments may provide informationthat may be useful to the surgeon in the procedure. For example, densityinformation of the donor tibia 505 may be obtained from the image and adesired portion of donor tibia 505 may be selected for grafting based,at least in part, on the density profile determined from the image. Inaddition, information regarding any imaged soft tissue attachments mayaid in planning placement of the soft tissue attachments with respect tothe patient's anatomy.

Whether or not donor tibia 505 is imaged, the surgeon may use processorbased system 36 to plan the surgical procedure on the patient's tibia405, including the step 220 of defining the volume and/or geometry ofthe resection of the patient's tibia 405. Based on this determination,haptic object 110 may be defined in step 230. For example, as shown inFIG. 4C, haptic object 110 may take the form of a boundary line distalto the fracture site 410. Processor based system 36 may include a numberof predefined geometries and/or volumes that may be utilized by thesurgeon in defining the haptic object 110. For example, in theillustrated example, the haptic object 110 includes a dovetail shapethat may provide a site with which the allograft may securely interlock.

The patient's tibia 405 is registered as described above in connectionwith step 240. A surgical tool 112, such as a drill, bur, or otherresecting tool, may be coupled to haptic device 113 and used to resecttibia 405 according to the surgical plan. As described above, the hapticdevice 113 may autonomously or semi-autonomously guide the surgical tool112 using the constraints of the haptic object 110 to remove the desiredgeometry and/or volume of bone, as shown in FIG. 4C. The path of the tipof the surgical tool 112 is tracked and information regarding the actualvolume of bone removed is stored in computer 36 and/or computer 10. Itis contemplated that the geometry and/or volume of tibia 405 removedwould be extremely close or identical to the surgical plan, althoughdeviations may be possible.

As the haptic device 113 resects tibia 405, data is stored in computer10 (and/or computer 36) to determine the geometry and/or volume of donortibia 505 that needs to be removed, as provided in step 260, in order toprovide a corresponding fit with the resected tibia 405. If not alreadyperformed, the donor tibia 505 is registered, for example in the samemanner in which the patient's tibia 405 was registered. The registrationtakes place after donor tibia 505 is securely positioned in holdingdevice 515 to help ensure that the global or real world coordinatesystem does not change with respect to the registered coordinate system,for example by unintentional movement of donor tibia 505 within holdingdevice 515. It should be noted that the holding device 515 may also beregistered during this step. Whether the registration is performedbefore or after the registration and resection of patient's tibia 405,the donor tibia 505 is resected using haptic device 113, as shown inFIG. 4E, so that the implantable portion 545 of donor tibia 505 has thedesired shape as defined in step 260. As noted above, instead of or inaddition to securing the donor tibia 405 in a holding device 515,tracking devices may be attached to the donor tibia 405 so that anymovement of the donor tibia 405, intentional or otherwise, is tracked bythe navigation system. With the donor tibia 505 resected, the surgeonmay implant the implantable portion 545 onto the resected portion of thepatient's tibia 405, in this case with a dovetail interlocking shape.Positioning of the implantable portion 545 or donor tibia 505 may becompleted manually, or with the aid of haptic device 113, for example byusing a clamp or other surgical tool 112 connected to haptic device 113to hold and position the implantable portion 545 or donor tibia 505 ontothe patient's resected tibia 405 with precision. If soft tissue, such asthe patellar tendon, was kept intact on the implantable portion 545 ofdonor tibia 505, that tendon may be attached to the patient and theprocedure completed. In other embodiments, repaired bone 505 withimplantable portion 545 positioned thereon may be imaged and modeled.The obtained images and/or model of the repaired bone may be compared toprevious models or surgical plans to determine whether a desiredsurgical result has been achieved. If additional changes to the repairbone are warranted, instructions may be sent to haptic device 113 toreorient implantable portion 545 on bone 505 or resect a portion ofimplantable portion 545 as required.

It should be understood that although a dovetail interlocking feature isdescribed above, other features of aiding implantation may be usedinstead or in addition. For example, other types of geometric keys,including tongue and groove, may be correspondingly formed in thepatient's tibia 405 and donor tibia 505. In fact, any correspondinggeometries intended to mate with one another may be created. Forexample, corresponding geometries that provide for a press fit and/orinterference fit may be created. Further, the donor bone may be resectedinto multiple pieces that fit together to form the desired implantshape. This type of procedure may be useful, for example, when a middleportion of a bone is being replaced, similar to the procedure describedin connection with FIGS. 3A-E. Still further, if the donor bone is to bescrewed to the patient's bone (or otherwise affixed with hardware),features to assist that fixation may be provided on the patient's boneand/or donor bone. For example, if a screw is to be used to screw thedonor bone into the patient bone, threaded screw holes or pilot holesmay be drilled into the donor bone by haptic device 113 to provide forimproved screw fixation of the donor bone to the patient's bone. Inaddition to, or alternatively to, any of the features described above,haptic device 113 may be programmed to create channels in the patient'sbone and/or the prosthesis so that bone cement or other adhesive may beplaced within the one or more channels to facilitate fixation of theprosthesis to the bone.

Still further, in some procedures one or more pieces of hardware, such abone plate, may be implanted to additionally secure other prostheticdevices, such as a donor bone or multiple pieces of donor bone. In somecases, a bone plate may be bent by the surgeon intraoperatively toprovide the best fit between the plate and the anatomy. However, suchbending is often done by trial and error. With the above disclosure inmind, if a surgeon bends a plate intraoperatively, the surgeon may probethe bone-contacting surface of the plate to determine the geometry ofthe surface, which may be compared by computer 10 and/or 36 to thesurface geometry of the patient anatomy to determine whether or not, andto what extent, the contour of the bone plate matches the contour of theanatomy to which the bone plate will be affixed.

Although the bulk allograft procedure is described above in relation toa tibia 405, it should be understood that the procedure applies to otherbones and to other types of resections. In addition, the procedure couldbe performed with the donor bone being a portion of the patient's ownbone from another site. With such an autograft procedure, the stepsoutlined above would be generally similar, but with the haptic device113 being used to resect the patient's host bone and also the patient'sown donor bone which may come from another part of the patient's body.

It should further be clear that the imaging and registration of thepatient's bone and donor bone may be performed essentially in any order.For example, the patient's bone may be imaged and registered, thenresected, and then the donor bone registered and resected.Alternatively, the patient and donor bone may both be registered priorto performing resection of either bone.

In addition, although the procedure described in connection with FIGS.4A-E uses a donor tibia 505 as a prosthesis, other prostheses, includingmetal and/or plastic prostheses, may be used to replace the resectedportion of the patient's tibia 405. For example, metal and/or plasticblank may be secured in holding device 515, with haptic device 113shaping the metal and/or plastic blank prosthesis to the desired shapeprior to implantation. Similarly, some groups of prostheses have similaror identical features to other groups of prostheses, with one group alsohaving additional features. For example, some knee implants have postsfor helping secure the implant to the bone, with other implants havingsimilar or identical features except the post is omitted. With suchgroups of prostheses, the type of prosthesis with the extra feature maybe stocked and secured in the holding device 515. If the surgeon desiresto use the implant with the additional feature, it may be otherwiseshaped based on the data obtained during bone removal. If the surgeondesires to use the implant but remove the additional feature (such asthe post), the post may additionally be removed through machining byhaptic device 113. This may reduce the number of types of prosthesesrequired to be stocked prior to a surgical procedure. The above conceptsare also applicable to the procedure described in connection with FIGS.3A-E, for example by shaping a porous metallic structure to replace thebone removed, with the void filler and/or bone growth composition beingadded to the metallic structure to complete the implantation.

Still further, although certain steps are described as being performedon processor based system 36 and/or computer 10, it should be understoodthat such steps may be performed on a separate computer device with theresults imported to processor based system 36 and/or computer 10. Forexample, the surgical plan may be created on a separate computer deviceprior to the surgery and the results of such plan imported to processorbased system 36 for use during the surgery.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims. For example,features described in relation to one embodiment may be combined withfeatures described in relation to another embodiment.

The invention claimed is:
 1. A method of performing a surgical procedureon a patient, comprising: planning a resection of a bone of the patient;while removing a volume of the bone with a surgical tool, tracking datacorresponding to a shape and volume of the removed bone with a computersystem operatively coupled to the surgical tool; after removing thevolume of the bone, determining a desired shape of a prosthesis to beimplanted into the removed volume of the bone based on the tracked datacorresponding to the shape and volume of the removed bone; and afterdetermining the desired shape of the prosthesis, forming the prosthesisand then implanting the prosthesis onto the bone of the patient.
 2. Themethod of claim 1, wherein planning the resection of the bone includesdetermining a planned volume of the bone to be removed.
 3. The method ofclaim 2, wherein the step of removing the volume of the bone with thesurgical tool is performed according to the planned volume of the boneto be removed.
 4. The method of claim 2, wherein the step of removingthe volume of the bone with the surgical tool is performed withdeviations from the planned volume of the bone to be removed.
 5. Themethod of claim 1, wherein the prosthesis is formed from allografttissue or autograft tissue.
 6. The method of claim 1, wherein theprosthesis is formed from metal or plastic.
 7. The method of claim 1,wherein the surgical procedure includes treatment of trauma to the bone.8. The method of claim 1, wherein the surgical procedure includes arevision of a previously implanted prosthesis.
 9. The method of claim 1,wherein the surgical procedure includes treatment of one or more tumors.10. The method of claim 9, wherein planning the resection of the bone ofthe patient includes imaging the bone, including a tumor site, andidentifying a boundary of the tumor site.
 11. The method of claim 10,wherein the step of identifying the boundary of the tumor site isperformed automatically based on bone density information or bonequality information from the imaging of the bone.
 12. The method ofclaim 1, wherein the surgical tool for removing the volume of the boneis operatively coupled to a robotic device during the removal step. 13.The method of claim 1, wherein forming the prosthesis includes shapingthe prosthesis using the surgical tool so that the prosthesis has ashape complementary to the shape of the removed bone.
 14. The method ofclaim 13, wherein the step of removing the volume of the bone includesforming a first geometric shape in the bone and the step of shaping theprosthesis includes forming a second geometric shape in the prosthesis,the first geometric shape being keyed to the second geometric shape. 15.The method of claim 14, wherein the first and second geometric shapesform a dovetail configuration.
 16. A method of performing a surgicalprocedure on a patient, comprising: tracking data, via a computersystem, corresponding to a shape and volume of a bone portion beingremoved from the patient with a surgical tool operatively coupled to thecomputer system and during the removal of the bone portion; and forminga prosthesis having a shape and volume based on the tracked data. 17.The method of claim 16, further comprising implanting the prosthesisagainst a resected bone of the patient.
 18. The method of claim 16,further comprising removing the bone portion with the surgical tool. 19.The method of claim 18, wherein the bone portion removed ispreoperatively planned.
 20. The method of claim 16, wherein theprosthesis forming step is performed intraoperatively.